Delay cap



June 26, 1934. J. STUART, 2D

DELAY CAP Filed Maron 51. 1952 fai/fw. 5e/D {Lf/W4 2 Patented `lune 26, 1934 DELAY CAP Joseph Stuart, 2d, Wilmington, Del., assgnor to Hercules Powder Company, Wilmington, Del., a corporation of Delaware Application March 31, 1932, Serial No. 602,133 v 3 Claims.

This invention relates to delay caps of the type used for firing commercial explosives and more particularly relates to an impro-vement in the fuse element positioned between the ignition head and the blasting cap.

Heretoiore delay caps, as is well known, have comprised an ignition head, or charge, a fuse and a cap or detonating charge. The fuse is arranged to be ignited by the ignition head and to ignite the cap and is cut to a length to give the desired delay.

In delay caps as known heretofore the fuse has been of the ordinary core type, that is to say, the

- burning element of the fuse, as for example, black powder, has formed a train centered within a tube or casing with the result that in order to provide caps having a material delay the assembly of ignition head, fuse and cap have to be oi considerable length, due to the necessity for the use of a substantial length of fuse. The excessive length of delay caps as heretofore provided is disadvantageous and undesirable.

Now in accordance with this invention, there is provided a delay cap of greatly decreased length for the longest desired delay and which may be made of a standard length over all for various different delay periods.

More particularly, in accordance with this invention there is provided a fuse or delay element which comprises a, core of suitable material provided with a spiral groove in which the burning v element or train is carried. Thus, as will be clear,

with a relatively short core the burning element or train may be of relatively great length and,

^ at the same time, trains of different length may be povided with cores of the same length,

The fuse element in accordance with this invention may be separately encased and secured to: an igniter head and to a cap, or it may be bodiment thereof with reference to the accompanying drawing, in which:

Figure 1 is a sectional view of a delay cap embodying this invention.

Figure 2 is an elevation of a fuse element (uncharged) embodying this invention.

Figure 3 is an elevation of a modification of the fuse element shown in Figure 2.

Figure 4 is a sectional View, broken away, of a modification of the delay cap shown in Figure 1.

Figure 5 is a sectional View, broken away, of

a further modification of the delay cap shown in Figure 1.

Referring to Figure 1, A indicates a casing of suitable material, as copper orgilding metal, usually employed for cap shells, at the bottom of which is positioned a detonating charge B of any suitable material customarily used in blasting caps, for example, a fulminate of .mercury-chlorate of pot-ash mixture, tetryl with a superimposed charge of lead azide resorcinate priming mixture trinitrotoluene with a superimposed priming charge of fulminate chlorate mixture, etc. C indicates a fuse element embodying this invention, placed on the detonating charge B. D indicates a charge of any usual or desirable ignition material, as for example a mixture of an oxidizing salt, nitrocellulose or nitrostarch, and a small amount of mercury fulminate, or an oxidizing salt, nitrocellulose or nitrostarch, and small amounts of diazodinitrophenol, or like ignition compounds, for ignition of the fuse. E indicates a sulphur plug, while F indicates any suitable waterproong material, and p indicates any suitable sealing material.

In the modilied form of delay blasting cap shown in Figure 4, y indicates a vent hole in the casing A for the escape of the gases of combustion of the fuse element, which vent is usually closed by a rupturable membrane of rubber or lacquer to prevent penetration of moisture before firing, and a indicates an empty compression space above the fuse. Such an assembly is employed when the fuse train is composed of a mixture resembling black powder, which on burning gives oil a large amount of gas.

Figure 5 indicates the delay cap assembly utilized when a ventless design is used with fuse compositions such as on burning will not generate any substantial quantity of gas, as, for example, a barium peroxideselenium mixture, and with the use of which no vent for the escape of gases of combustion is necessary, but an enlarged compression space. e is provided to lessen the bursting shock on the walls of the cap shell exerted by ignition of the flash composition D.

Lead wires G, adapted to be connected into an electric circuit, extend into the ignition charge D, their ends being connected by a bridge wire H, adapted to heat on the passage of a current and to ignite the igniter charge D.

Referring now to Figure 2, the fuse element C comprises a core z' of any suitable material, as, for example, aluminum, copper, asbestos, etc., provided with a spiral groove in its surface. The spiral groove y is desirably, though not neces* lead-sulfur mixture, etc.

. the fuse shown in Figure 4 may, for example, be

formed of black powder, while the powder train 1c in the ventless type caps, shown in Figures 1 and 5 will be composed, for example, of barium peroxide-selenium or red lead-sulfur mixtures. The core i, with a train lc in the spiral groove 1i, is encased by a close tting sleeve of light metal or other suitable material, as asbestos, etc., indicated at L, Figure 2, to prevent jumping of the' re in the train from turn to turn of the spiral, or the core may be made to t closely in the casing A, and the sleeve L omitted, as shown in Figure l. p l

Referring now to Figure 3, the core :i may be provided with two or more spiral grooves m and n, connected at thepoint of ignition, so that if the train in one goes out, continued burning of the other will re the detonating capl or charge.

The train k may be loaded into` the groove or grooves in the core in any suitablermanner, as, Vfor example, manually, or by pressing in Awith rollers. It will be noted that where the walls of the groove or grooves are uundercut the train will bevbetter retained than if they be straight-walled.

As will be now observed, the length of the fuse train may be made relatively long with a relatively short fuse core by merely increasing the number of turns of the groove i and, at the same time, with a given length of core various lengths of train may be provided by varying the number of turns of the groove y.

It will be appreciated that the fuse element in accordance with this invention may be variously constructed, and may be incorporated variously with the elements of a delay cap, and that this invention is not intended to be in any wise limited to the embodiments thereof described and illustrated herein.

What I claim and desire to protect by Letters Patent is:

1. Ay fuse element for delay caps including a core provided with a spiral groove in its outer surface, the walls of the groove being undercut and a powder train within the groove.

2. A` fuse element for delay caps including a core provided with a groove in its outer surface, the walls of the groove being undercut and a powder train within the groove.

3. A fuse element for delay Vcaps including a core vprcvidedwith an open grceve in its cuter surface and extending from end to end of the core, the walls of the groove being undercut, and a fuse powder compressed within and completely filling the groove.

JOSEPH STUART, II. 

